Using the same principle as the LED strobes that enable fine-tuning of turntable rotation speeds, this DIY "Acid Machine" synth has a cool way of visualizing its sound: A rotating disc printed with a special pattern isolates a thin radial disc depending on the frequency of a strobing LED that corresponds to the note played. You can use it to tune the synth itself (as seen in the beginning of the following video) for traditionally trippy early-Aphex acid tones, or to squeeze secrets out of your enemies once they're sufficiently hypnotized by the spinning visualizer. Yes, relax, and stare into the wheel...
[Gieskes.nl via MAKE]